An impairment rating is a formal medical assessment that quantifies the degree of permanent functional loss an individual has sustained due to an injury or illness. Conducted by a physician, this assessment provides an objective, standardized measure of a patient’s physical or mental limitations. The finding is expressed as a percentage, reflecting the severity of the loss of normal body function. This percentage is a clinical statement about physical condition, not a direct measure of the inability to work.
Defining the Medical Impairment Rating
A medical impairment rating measures the loss of use of a specific body part or the function of an organ system resulting from a health condition. It is a purely medical conclusion about a patient’s health status, independent of their occupation, age, or ability to earn an income. It addresses physical or psychological damage to the body’s structures or functions, such as a reduced range of motion or a measurable deficit from nerve damage.
The physician only calculates this rating after the patient has reached Maximum Medical Improvement (MMI). MMI is the point when the patient’s medical condition has stabilized and is not expected to improve substantially with further treatment. This means the condition has reached a plateau, signaling that any remaining limitations are permanent. An impairment is defined as permanent damage to the body after MMI has been established.
Standardized Assessment Methodology
The process for calculating an impairment rating is standardized to ensure consistency across different medical evaluations. Ratings are performed by licensed physicians, often specialists like orthopedic surgeons or occupational medicine doctors, who have specific training in this area. The standard reference used by medical evaluators in most jurisdictions is the American Medical Association’s Guides to the Evaluation of Permanent Impairment, commonly known as the AMA Guides.
The AMA Guides provide physicians with specific criteria, measurement techniques, and tables for various types of injuries and conditions. For musculoskeletal injuries, this often involves objective measurements of a joint’s range of motion or manual muscle strength testing. These measurements are then matched to corresponding impairment values in the Guides’ tables to arrive at a whole-person impairment percentage.
Different jurisdictions may mandate the use of a specific edition of the AMA Guides, such as the Fourth, Fifth, or Sixth Editions. This can lead to variations in the final rating depending on the year of the injury and the location of the claim.
Distinguishing Impairment from Disability
One common source of confusion is the difference between medical impairment and legal or economic disability. Impairment is a medical term that quantifies a loss of function within the body itself. It is an objective assessment of the physical or mental condition, such as a 15% loss of use of a leg.
Disability, by contrast, is a legal or administrative determination that assesses an individual’s inability to perform specific job duties or engage in gainful employment due to their medical impairment. This determination goes beyond the medical findings and incorporates vocational factors, including education, age, work history, and the specific demands of their job. An impairment rating may be the same as someone else’s, but the disability status can be completely different based on these non-medical factors.
For example, a concert pianist and a delivery driver may both receive a 10% impairment rating for a hand injury. However, the pianist’s inability to perform their specialized work will likely result in a much higher disability classification than the driver’s, whose job may be less impacted. This distinction emphasizes that a medical impairment rating is only one component used in the broader calculation of a person’s legal disability status.
Role of the Rating in Legal and Insurance Contexts
Once the physician certifies the impairment rating, the percentage becomes the foundation for determining financial compensation in various legal and insurance contexts. The most frequent application is in workers’ compensation systems, where the rating is used to calculate Permanent Partial Disability (PPD) benefits. The rating may also be a factor in personal injury lawsuits or federal programs, such as those for veterans’ benefits.
In the context of PPD, the impairment percentage is not the final compensation amount but is instead a primary variable in a statutory formula. Jurisdictions use the percentage to determine the amount of benefits, often by multiplying the rating by a fixed dollar value or a predetermined number of weeks of compensation. This calculation translates the medical finding of functional loss into a specific financial award for the injured party.
The final benefit amount is a product of the physician’s medical finding and the specific legal rules governing the claim. The impairment rating serves as the objective medical baseline that anchors the entire process. The rating is influential in settlement negotiations, as it provides a concrete figure for the insurance company and the claimant to use in valuing the case.